[Bugfix] Abort requests when the connection to /v1/completions is interrupted

[chestnut-Q]

When the connection to /v1/completions is interrupted, the corresponding requests are not aborted. An exception handling (for asyncio.CancelledError) is needed in merge_async_iterators to fix this bug.

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[DarkLight1337]

Looks good, maybe also add a note to remind devs to add msg parameter when Python 3.9 becomes the minimum supported version.

[njhill]

Thanks @chestnut-Q this looks great.

I think the problem may also be due to the fact that in serving_completion.py when the client disconnects, only one of the sub-requests is aborted.

But this change is good to have regardless.

Would you be willing to add a unit test, even if just testing merge_async_iterators cancellation propagation in isolation?

[chestnut-Q]

Thanks @chestnut-Q this looks great.

I think the problem may also be due to the fact that in serving_completion.py when the client disconnects, only one of the sub-requests is aborted.

But this change is good to have regardless.

Would you be willing to add a unit test, even if just testing merge_async_iterators cancellation propagation in isolation?

Thanks for reviewing and for the suggestion, @njhill. I think the problem stems from the asyncio.CancelledError in await queue.get() not propagating to _tasks, which results in the request not being aborted even if there is only one sub-request in request.

I've added a unit test for the cancellation propagation of merge_async_iterators. Please take a look and let me know if there are any further adjustments you'd like to see.

[njhill]

Thanks @chestnut-Q, just a couple of small comments on the test